Turbine blade attachment curved rib stiffeners

ABSTRACT

The present disclosure provides a fir tree coupling for gas turbine engine parts comprising a load beam having a longitudinal axis, a rounded base, a first side, and a second side, wherein the rounded base has a radius of curvature from the first side to the second side, a tooth running parallel to the longitudinal axis and disposed on the first side of the load beam. The fir tree coupling may comprise a channel through the rounded base across a portion of the radius of curvature from the first side to the second side. The channel may comprise a sidewall having a sidewall step cut into a portion of the channel sidewall.

FIELD

The present disclosure relates to gas turbine engines, and morespecifically, to turbine blade to disk interface and attachmentstructures.

BACKGROUND

Low Cycle Fatigue (LCF) is a failure mechanism that may limit thein-service life of turbine airfoils, such as blades. Cracks may beinitiated by LCF in turbine airfoils after a number of engine cycles.High stresses may arise due to the geometry of the turbine airfoil. In‘fir tree’ type couplings between a turbine disk and a turbine blade,these stresses often arise in the attachment fillets adjacent to(radially outboard of) the blade-disk bearing surface.

SUMMARY

In various embodiments, the present disclosure provides a fir treecoupling comprising a load beam having a longitudinal axis, a roundedbase, a first side, and a second side, wherein the rounded base has aradius of curvature from the first side to the second side, a toothrunning parallel to the longitudinal axis and disposed on the first sideof the load beam.

In various embodiments, the fir tree coupling comprises a channelthrough the rounded base across a portion of the radius of curvaturefrom the first side to the second side. In various embodiments, thechannel comprises a sidewall having a sidewall step cut into a portionof the channel sidewall. In various embodiments, the channel comprisesat least one of a concave sidewall having a concave curvature into therounded base, a vertical sidewall extending perpendicular into therounded base, or a wide channel wherein the wide channel extends acrossthe length of the load beam between a first portion at a first end ofthe wide channel and a second portion at a second end of the widechannel. In various embodiments, the channel comprises a taperedsidewall wherein the tapered sidewall extends at an angle into therounded base. In various embodiments, the channel is disposed at anangle to the longitudinal axis of the load beam. In various embodimentsthe tooth includes a bearing surface. In various embodiments, the loadbeam comprises a top surface and a cooling passage passing through theload beam from the rounded base to the top surface. In variousembodiments, the load beam comprises at least one of nickel, nickelalloy, titanium, or titanium alloy. In various embodiments, the loadbeam comprises a monocrystalline material.

In various embodiments, the present disclosure provides a blade assemblyfor a gas turbine engine comprising a platform having a dorsal surfaceand ventral surface, an airfoil extending from the dorsal surface, a firtree coupling extending from the ventral surface, the fir tree couplingcomprising a load beam having a longitudinal axis, a rounded base, afirst side, and a second side, wherein the rounded base has a radius ofcurvature from the first side to the second side, a tooth runningparallel to the longitudinal axis and disposed on the first side of theload beam.

In various embodiments, the fir tree coupling comprises a channelthrough the rounded base across a portion of the radius of curvaturefrom the first side to the second side. In various embodiments, thechannel comprises a sidewall having a sidewall step cut into a portionof the channel sidewall. In various embodiments, the channel comprisesat least one of a concave sidewall having a concave curvature into therounded base, a vertical sidewall extending perpendicular into therounded base, or a wide channel wherein the wide channel extends acrossthe length of the load beam between a first portion at a first end ofthe wide channel and a second portion at a second end of the widechannel. In various embodiments, the channel comprises a taperedsidewall wherein the tapered sidewall extends at an angle into therounded base. In various embodiments, the channel is disposed at anangle to the longitudinal axis of the load beam. In various embodiments,the fir tree coupling comprises a first cooling passage in fluidcommunication with a second a cooling passage within at least one of theplatform or the airfoil. In various embodiments, the fir tree couplingcomprises at least one of nickel, nickel alloy, titanium, or titaniumalloy. In various embodiments, the fir tree coupling comprises amonocrystalline material.

In various embodiments, the present disclosure provides a method ofmanufacturing a fir tree coupling comprising forming a load beam havinga longitudinal axis, a rounded base, a first side, a second side, and atooth running parallel to the longitudinal axis and disposed on thefirst side of the load beam. In various embodiments, the method furthercomprises forming a radius of curvature on the rounded base from thefirst side to the second side. In various embodiments, the methodfurther comprises forming a channel through the rounded base across aportion of the radius of curvature from the first side to the secondside of the load beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a gas turbine engine;

FIG. 2 illustrates a blade assembly, in accordance with variousembodiments;

FIG. 3 illustrates a blade assembly at the blade-disk attachment region,in accordance with various embodiments;

FIG. 4 illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments;

FIG. 5A illustrates the base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 5B illustrates a section through the blade-disk attachment regionwithin a channel through the rounded base of a fir tree coupling, inaccordance with various embodiments;

FIG. 5C illustrates the base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 6A illustrates the profile of a blade assembly having channelsthrough the rounded base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 6B illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments;

FIG. 7A illustrates the profile of a blade assembly having channelsthrough the rounded base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 7B illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments;

FIG. 8A illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments;

FIG. 8B illustrates the profile of a blade assembly having channelsthrough the rounded base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 9A illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments;

FIG. 9B illustrates the profile of a blade assembly having channelsthrough the rounded base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 10A illustrates the profile of a blade assembly having channelsthrough the rounded base of a fir tree coupling, in accordance withvarious embodiments;

FIG. 10B illustrates a perspective view of a fir tree type coupling, inaccordance with various embodiments; and

FIG. 11 illustrates a method of manufacturing a fir tree coupling, inaccordance with various embodiments.

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that logical changes and adaptations in design andconstruction may be made in accordance with this disclosure and theteachings herein. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation. The scope of thedisclosure is defined by the appended claims. For example, the stepsrecited in any of the method or process descriptions may be executed inany order and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact. Surface shading lines may be used throughout thefigures to denote different parts but not necessarily to denote the sameor different materials. In some cases, reference coordinates may bespecific to each figure.

All ranges and ratio limits disclosed herein may be combined. It is tobe understood that unless specifically stated otherwise, references to“a,” “an,” and/or “the” may include one or more than one and thatreference to an item in the singular may also include the item in theplural.

With reference to FIG. 1, an exemplary gas turbine engine 2 is provided.Gas turbine engine 2 is a two-spool turbofan that generally incorporatesa fan section 4, a compressor section 6, a combustor section 8 and aturbine section 10. Vanes 51 may be disposed throughout the gas turbineengine 2. Alternative engines include, for example, an augmentor sectionamong other systems or features. In operation, fan section 4 drives airalong a bypass flow-path B while compressor section 6 drives air along acore flow-path C for compression and communication into combustorsection 8 then expansion through turbine section 10. Although depictedas a turbofan gas turbine engine 2 herein, it should be understood thatthe concepts described herein are not limited to use with turbofans asthe teachings is applicable to other types of turbine engines includingthree-spool architectures. A gas turbine engine may comprise anindustrial gas turbine (IGT) or a geared aircraft engine, such as ageared turbofan, or non-geared aircraft engine, such as a turbofan, ormay comprise any gas turbine engine as desired.

Gas turbine engine 2 generally comprises a low speed spool 12 and a highspeed spool 14 mounted for rotation about an engine central longitudinalaxis X-X′ relative to an engine static structure 16 via several bearingsystems 18-1, 18-2, and 18-3. It should be understood that bearingsystems is alternatively or additionally provided at locations,including for example, bearing system 18-1, bearing system 18-2, andbearing system 18-3.

Low speed spool 12 generally comprises an inner shaft 20 thatinterconnects a fan 22, a low pressure compressor section 24, e.g., afirst compressor section, and a low pressure turbine section 26, e.g., asecond turbine section. Inner shaft 20 is connected to fan 22 through ageared architecture 28 that drives the fan 22 at a lower speed than lowspeed spool 12. Geared architecture 28 comprises a gear assembly 42enclosed within a gear housing 44. Gear assembly 42 couples the innershaft 20 to a rotating fan structure. High speed spool 14 comprises anouter shaft 80 that interconnects a high pressure compressor section 32,e.g., second compressor section, and high pressure turbine section 34,e.g., first turbine section. A combustor 36 is located between highpressure compressor section 32 and high pressure turbine section 34. Amid-turbine frame 38 of engine static structure 16 is located generallybetween high pressure turbine section 34 and low pressure turbinesection 26. Mid-turbine frame 38 supports one or more bearing systems18, such as 18-3, in turbine section 10. Inner shaft 20 and outer shaft80 are concentric and rotate via bearing systems 18 about the enginecentral longitudinal axis X-X′, which is collinear with theirlongitudinal axes. As used herein, a “high pressure” compressor orturbine experiences a higher pressure than a corresponding “lowpressure” compressor or turbine.

The core airflow C is compressed by low pressure compressor section 24then high pressure compressor section 32, mixed and burned with fuel incombustor 36, then expanded over high pressure turbine section 34 andlow pressure turbine section 26. Mid-turbine frame 38 includes surfacestructures 40, which are in the core airflow path. Turbines 26, 34rotationally drive the respective low speed spool 12 and high speedspool 14 in response to the expansion.

Gas turbine engine 2 is, for example, a high-bypass geared aircraftengine. The bypass ratio of gas turbine engine 2 is optionally greaterthan about six (6). The bypass ratio of gas turbine engine 2 isoptionally greater than ten (10). Geared architecture 28 is an epicyclicgear train, such as a star gear system, e.g., sun gear in meshingengagement with a plurality of star gears supported by a carrier and inmeshing engagement with a ring gear, or other gear system. Gearedarchitecture 28 has a gear reduction ratio of greater than about 2.3 andlow pressure turbine section 26 has a pressure ratio that is greaterthan about five (5). The bypass ratio of gas turbine engine 2 is greaterthan about ten (10:1). The diameter of fan 22 is significantly largerthan that of the low pressure compressor section 24, and the lowpressure turbine section 26 has a pressure ratio that is greater thanabout 5:1. Low pressure turbine section 26 pressure ratio is measuredprior to inlet of low pressure turbine section 26 as related to thepressure at the outlet of low pressure turbine section 26 prior to anexhaust nozzle. It should be understood, however, that the aboveparameters are exemplary of a suitable geared architecture engine andthat the present disclosure contemplates other turbine engines includingdirect drive turbofans.

An engine 2 may comprise a rotor blade 68 or a stator vane 51. Statorvanes 51 may be arranged circumferentially about the engine centrallongitudinal axis X-X′. Stator vanes 51 may be variable, meaning theangle of attack of the airfoil of the stator vane may be variablerelative to the airflow proximate to the stator vanes 51. The angle ofattack of the variable stator vane 51 may be variable during operation,or may be fixable for operation, for instance, being variable duringmaintenance or construction and fixable for operation. In variousembodiments, it may be desirable to affix a variable vane 51 in fixedposition (e.g., constant angle of attack).

In various embodiments, a fir tree coupling is disclosed for interfacingan airfoil (e.g., a blade) with a turbine disk of a gas turbine engine.A fir tree coupling, according to various embodiments, may comprise aload beam having a longitudinal axis, a rounded base, a first side, anda second side. In various embodiments, the rounded base may have aradius of curvature. The fir tree coupling may comprise a plurality ofteeth running parallel or substantially parallel to the load beamlongitudinal axis and disposed on the first side and the second side ofthe load beam. In various embodiments, the teeth have bearing surfaceswhich transmit loads at the blade-disk interface. The blade-diskinterface load may be concentrated as a high stress in an attachmentfillet disposed between the teeth of the fir tree coupling. The roundedbase of the fir tree coupling may comprise a radius of curvature betweenthe first side and the second side which may reduce attachment filletstress and tend to mitigate LCF.

In various embodiments, a blade assembly may comprise a fir treecoupling, an airfoil, and a platform having a dorsal and a ventralsurface. The airfoil extends from the dorsal surface of the platform andthe fir tree coupling extends from the ventral surface of the platform.The blade assembly is coupled to a turbine disk by the fir tree couplingwhich transmits the centrifugal force acting on the airfoil resultingfrom the airfoil's rotation about the gas turbine engine shaft to theturbine disk through the bearing surfaces of the fir tree couplingteeth. The centrifugal force induces bending in the teeth which tends toconcentrate stresses at the lower most attachment fillet between theteeth. The aforesaid stress concentrations may propagate cracking whichtends to drive LCF. In various embodiments, the rounded base of the firtree coupling tends to resist tooth bending by compression of therounded base material across the radius of curvature reducing attachmentfillet stresses, and thereby tending to mitigate LCF.

With reference now to FIG. 2, in accordance with various embodiments, ablade assembly 100 comprises an airfoil 102, a platform 104, and a firtree coupling 200. Airfoil 102 extends from dorsal surface 106 ofplatform 104. Fir tree coupling 200 includes teeth 202 and rounded base210 and extends from ventral surface 108 of platform 104. Xyz axes areshown for convenience, with z extending perpendicular to the xy plane.In that regard, a measurement point displaced in the positive z-axisdirection from a given reference point may be considered “above” or on“top” of the given reference point. In contrast, a measurement pointdisplaced in the negative z-axis direction from the given referencepoint may be considered “below” or on “bottom” of the given referencepoint. In that regard, the terms “top” and “bottom” may refer torelative positions along the z-axis. For example, airfoil 102 is on topof platform 104 and fir tree coupling 200 is below airfoil 102. Channels204 are cut in the rounded base 210 of fir tree coupling 200.

With reference now to FIG. 3, a blade-disk attachment region, inaccordance with various embodiments, is shown. Blade assembly 100 isinserted into turbine disk 301 and coupled by fir tree coupling 200. Asdisk 301 rotates at high speed, centrifugal force 300 is generated,which is transmitted into disk 301 at bearing surfaces 203 of teeth 202,tending to induce bending 302, which tends to concentrate stress atattachment fillets 304. The compressive force 303 is resisted by roundedbase 210 and tends to reduces stress at attachment fillets 304.

In various embodiments and with reference now to FIG. 4, a fir treecoupling 200 is shown to comprise a load beam 206 having a first side212 and a second side 214, a rounded base 210 having a radius ofcurvature 211 from the first side 212 to the second side 214, and alongitudinal axis 207. In various embodiments, the load beam may furthercomprise a top surface 208. In various embodiments, a plurality of teeth202 having bearing surface 203 proximate attachment fillet 304 aredisposed on the first side 212 and the second side 214 extend laterally(along the y-axis) and run parallel to the longitudinal axis 207 (alongthe x-axis). Channels 204 are cut across the radius of curvature 211 ofrounded base 210 and extend between the first side 121 and second side214 of the load beam.

In various embodiments, a fir tree coupling may be made of metal, analloy, nickel, nickel alloy, titanium, or titanium alloy. In variousembodiments, a fir tree coupling may be surface treated or may be heattreated by precipitation hardening or age hardening. In variousembodiments, a fir tree coupling may be a precipitation-hardeningaustenite nickel-chromium superalloy such as that sold commercially asInconel®. In various embodiments, a fir tree coupling may be a singlecrystal or monocrystalline solid.

In various embodiments and with reference now to FIGS. 2, 5A and 5B,cooling passages 216 in the rounded base of a fir tree coupling such asrounded base 210 may be disposed within channels 204 and extend upward(along the z-axis) from the base through the load beam to a top surfacesuch as top surface 208 of a fir tree coupling. Cooling passages 216extend radially outward through the airfoil. Cooling passages 216 mayhave an opening in a rounded base such as rounded base 210 or a in floorof a channel such as channel 204 and may form part of a cooling systemfor a blade assembly such as blade assembly 100 and be in fluidcommunication with a second cooling passage disposed within a platformsuch as platform 104 or an airfoil such as airfoil 102.

In various embodiments and with reference now to FIGS. 5A and 5C,channels such as channels 204 may be perpendicular to the longitudinalaxis of a load beam such as longitudinal axis 207. In variousembodiments, channels such as channel 218 may be disposed at an angle tothe longitudinal axis of a load beam such as longitudinal axis 207.Cooling passages 216 may be skewed relative to the longitudinal axis.

In various embodiments and with reference now to FIGS. 6A and 6B, ablade assembly 600 comprises fir tree coupling 602. Fir tree coupling602 comprises vertical channels 604 across a portion of the length ofthe load beam which comprise a vertical sidewall 620 extending into therounded base perpendicular to the rounded base.

In various embodiments and with reference now to FIGS. 7A and 7B, ablade assembly 700 comprises fir tree coupling 702. Fir tree coupling702 comprises single, wide channel 722 through the rounded base whereinthe wide channel extends nearly the entire length of the load beamexcept for a first portion 724 and/or a second portion 726 of roundedbase left at either end of the wide channel.

In various embodiments and with reference now to FIGS. 8A and 8B, ablade assembly 800 comprises fir tree coupling 802. Fir tree coupling802 comprises stepped channels 804 which comprise a sidewall having asidewall step 224 cut into a portion of the channel sidewall. In variousembodiments, multiple sidewall steps may be present.

In various embodiments and with reference now to FIGS. 9A and 9B, ablade assembly 900 comprises fir tree coupling 902. Fir tree coupling902 comprises channels 904 which comprise a concave sidewall 226 havinga concave curvature into the rounded base.

In various embodiments and with reference now to FIGS. 10A and 10B, ablade assembly 1000 comprises fir tree coupling 1002. Fir tree coupling1002 comprises tapered channels 1004 which comprise a tapered sidewall228 wherein the tapered sidewall extends at an angle into the roundedbase.

In various embodiments and with reference now to FIG. 11, a method 1100of manufacturing a fir tree coupling may comprise forming a load beam1102 having a longitudinal axis, a rounded base, a first side, a secondside, and a tooth running parallel to the longitudinal axis and disposedon the first side of the load beam and, forming a radius of curvature1104 on the rounded base from the first side to the second side. Formingmay comprise subtractive manufacturing such as casting, forging,milling, grinding, machining, and the like. Forming may also compriseadditive manufacturing such as electron-beam melting, selective lasersintering, electron-beam freeform fabrication, and the like. Forming mayalso comprise joining, such as welding, brazing and/or other suitablemethods. The method may further comprise forming a channel 1106 throughthe rounded base across a portion of the radius of curvature from thefirst side to the second side of the load beam.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A fir tree coupling comprising: a load beamhaving a longitudinal axis, a rounded base, a first side, and a secondside, wherein the rounded base has a radius of curvature from the firstside to the second side, a tooth running parallel to the longitudinalaxis and disposed on the first side of the load beam, and a plurality ofchannels, extending transverse to the longitudinal axis from the firstside to the second side of the load beam, defining a plurality ofrounded base portions therebetween.
 2. The fir tree coupling of claim 1,wherein the plurality of channels comprises a sidewall having a sidewallstep cut into a portion of the sidewall.
 3. The fir tree coupling ofclaim 1, wherein the plurality of channels comprises at least one of aconcave sidewall having a concave curvature into the plurality ofrounded base portions or a vertical sidewall extending perpendicularinto the rounded base from the plurality of rounded base portions. 4.The fir tree coupling of claim 1, wherein the plurality of channelscomprises a tapered sidewall wherein the tapered sidewall extends at anon-orthogonal angle into the rounded base from the plurality of roundedbase portions.
 5. The fir tree coupling of claim 1, wherein theplurality of channels is disposed at a non-orthogonal angle to thelongitudinal axis of the load beam.
 6. The fir tree coupling of claim 1,wherein the tooth includes a bearing surface.
 7. The fir tree couplingof claim 1, wherein the load beam comprises a top surface and a coolingpassage passing through the load beam from the rounded base to the topsurface.
 8. The fir tree coupling of claim 1, wherein the load beamcomprises at least one of nickel, nickel alloy, titanium, or titaniumalloy.
 9. The fir tree coupling of claim 1, wherein the load beamcomprises a monocrystalline material.
 10. A turbine blade assembly for agas turbine engine comprising: a platform having a dorsal surface and aventral surface; a turbine blade extending from the dorsal surface; afir tree coupling extending from the ventral surface, the fir treecoupling comprising a load beam having a longitudinal axis, a roundedbase, a first side, and a second side, wherein the rounded base has aradius of curvature from the first side to the second side, a toothrunning parallel to the longitudinal axis and disposed on the first sideof the load beam, and a plurality of channels, extending transverse tothe longitudinal axis from the first side to the second side of the loadbeam, defining a plurality of rounded base portions therebetween. 11.The turbine blade assembly of claim 10, wherein the plurality ofchannels comprises a sidewall having a sidewall step cut into a portionof the sidewall.
 12. The turbine blade assembly of claim 10, wherein theplurality of channels comprises at least one of a concave sidewallhaving a concave curvature into the plurality of rounded base portionsor a vertical sidewall extending perpendicular into the rounded basefrom the plurality of rounded base portions.
 13. The turbine bladeassembly of claim 10, wherein, the plurality of channels comprises atapered sidewall wherein the tapered sidewall extends at anon-orthogonal angle into the rounded base from the plurality of roundedbase portions.
 14. The turbine blade assembly of claim 10, wherein theplurality of channels is disposed at a non-orthogonal angle to thelongitudinal axis of the load beam.
 15. The turbine blade assembly ofclaim 10, wherein the fir tree coupling comprises at least one ofnickel, nickel alloy, titanium, or titanium alloy.
 16. The turbine bladeassembly of claim 10, wherein the fir tree coupling comprises amonocrystalline material, wherein the fir tree coupling comprises afirst cooling passage in fluid communication with a second coolingpassage within at least one of the platform or the turbine blade.
 17. Amethod of manufacturing a fir tree coupling comprising: forming a loadbeam having a longitudinal axis, a rounded base, a first side, a secondside, and tooth running parallel to the longitudinal axis and disposedon the first side of the load beam, forming a radius of curvature on therounded base from the first side to the second side, and forming aplurality of channels, extending transverse to the longitudinal axisfrom the first side to the second side of the load beam and across theradius of curvature, defining a plurality of rounded base portionstherebetween.
 18. The method of claim 17, wherein the plurality ofchannels is disposed at a non-orthogonal angle to the longitudinal axisof the load beam.